Using PhotoDNA, the system picks out images which are identical, even if they have been edited, resized, cropped and edited in other ways, and logs them. The system matches them through a technique which monochromes the image, breaks the image into smaller chunks and the intensity gradients are converted into a signature.

The signatures, even through editing, will remain the same and allow the system to find copies of the original image. Some similarities could compare QR codes to this, allowing similar cells to match other images, allowing the system to recognise similar gradients and therefore image copies across massive sets of data.

The ISPs are then given a list of these signatures, data strings essentially without giving away evidence, to search for other identical images which are out there on the web. The accuracy rating stands at 92% while false positives only delivers less than one in a billion images.

Microsoft is donating this technology to the NCMEC, which will then be licenced out to other law enforcement agencies across the globe.

This isn't new technology as such. Similar technologies have been developed to identify parts of images, such as skin tones, shadows, identifiable features within the image and lighting to determine whether other images took place from within that same area. This allows collections of images to be stored and categorised and used against the perpetrators in a court of law as mounted evidence.

While this could well be used in closed, internal networks of law enforcement to determine the same victim across multiple situations and abusers, this system could also be enabled to comb the Internet and ISP networks for similar content.

To make this fully effective, government policy needs to be introduced to mandate ISPs and content providers to employ these technologies, even though most US ISPs already work with NCMEC to create safer networks.

This technology seems to be in the second major development after CETS, the Child Exploitation Tracking System, which lets agencies share information using web based technologies to allow interoperability and collaboration across borders.

On a personal note, Microsoft seems to be donning the hat of morals with this technology. It's admirable to see the company working with law enforcement agencies to combat the ever growing threat of online child abuse, and this technology will surely make a massive difference.